Reversible tape transport system



United States ate t Don C. Barnett; Kingston E. Ganske, Columbus, Ind.[21] Appl.No. 758,061

{72] Inventors [54] REVERSIBLE TAPE TRANSPORT SYSTEM 3 Claims, 6 DrawingFigs.

[52] U.S.Cl 274/4, 226/42: 179/1002 51 mac: Gllb 5/00 [50] FieldofSearch 242/192:

179/100.2CA; 274/4A, 11A; 226/42, 30, 31(lnquired): 340/174.1(lnquired):178(NA);

3 24/ inquired) [56] References Cited UNITED STATES PATENTS 3,419,68612/1968 Rho ades 179/1002 3.449.528 6/1969 Camras 3,487,175 12/1969Newell Primary Examiner-Leonard Forman Assistant Examiner-Dennis A.Dearmg Attorney-Marechal, Biebel. French & Bugg ABSTRACT: A transportfor flexible tape employs a reversible rotatable capstan with rolls onopposite sides mounted on axes parallel to the axis of rotation of andmovable toward and away from the capstan as tape is moved from one rollto the other. Whichever roll is functioning as a takeup is frictiondriven by the capstan. A synchronous motor drives the capstan; it has agovernor control for slow speed operation and a resonant damper tominimize velocity changes at running speed. When used as a multitracklongitudinal recorder, the transducer is shifted to follow a differenttrack at each direction change when most of the tape is wound on one ofthe rolls; this shift can be initiated by the motor governor control.

vmmfin'nmsmm 3,550,985

SHEET 1 OF 3 INVENTORS DON C. BARNETT & KINGSTON E. GANSKE ATTORNEYSPATENTEuniczelsm 3.550.985

I sum 2 OF 3 r FIG-3 I 'lf I g]; IIO I071 us ||7'\'V I22} v 5 4 HEADSHIFT common.

PATENTED 05:29 1970 SHEET 3 OF 3 P F lG-G.

START STOP MW 1-84 I IL,

T? HEAD SHIFT CONTROL? (FIG-3) CROSS REFERENCE TO RELATED APPLICATIONSThe invention disclosed and claimed in this application is related tothe disclosures of copending applications Ser. No. 644,015, filed June6, 1967, Ser. No. 705,478, filed on Feb. 14, 1968 now US. Pat. No.3,489,369, and Ser. No. 705,479, filed on Feb. 14, 1968, all assigned tothe same assignee as this application.

BACKGROUND OF THE INVENTION This invention relates to reversible tapetransport systems, particularly as used in magnetic recording. Theparticular form of transport system involved uses a reversible rotatablecapstan driven by a synchronous motor and arranged to pass tape from oneroll to another in either direction. The rolls are mounted to rotateabout axes parallel to the rotational axis of the capstan, and theseaxes or hubs are mounted to move toward and away from the capstan as thetape is transferred from one roll to the other, the thus changing thesize of the rolls. Either roll operates as a supply or a takeup,depending upon the direction of operation. That roll functioning at anytime as a takeup is friction driven by the capstan, while that rollfunctioning as a supply is held in somewhat spaced relationship from thecapstan surface until it is time to reverse and the supply thus becomesthe takeup.

It has been rather customary in other forms of transports to employ arather large and heavy flywheel to assure a constant rotational velocityof the capstan. The inertia of such a flywheel is, however, basicallyincompatible with the requirements of a system for rapidly reversing thedirection of tape movement. Without a flywheel, various servocontrolshave been suggested to assure a constant velocity, but such controls arecomplicated and expensive. It has been found that by em ploying a drivefrom a synchronous motor, using a resonant damper to minimize anyvelocity changes in the motor output, the desired constant tape speedcan be achieved. This is important where one or more magnetictransducers cooperate with magnetic recording tape being moved by thecapstan surface; particularly in video tape recording systems, absolutecontrol over tape velocity is essential to eliminate time base errors.

To provide an effective longitudinal recording video tape recordersystem, it is desirable to have multiple tracks usable from the tape,and to move the transducer head to scan different tracks on the tapeineach direction. Thus, tape from the initial supply roll is transportedpast the transducer to the takeup with the head scanning one track. Asthe end of the tape comes near, the capstan direction is rapidlyreversed and the supply roll becomes the takeup. and during the rapidreversal the head is shifted to another track. This operation can berepeated a number of times. For example, in a successful embodiment ofthe invention tape is transported at a speed in the order of 120-160inches per second in one direction, giving a recording time of about 6minutes, then the tape direction is re versed and the head moved, tooperate in the opposite direction for the same amount of time, and soon. It has been possible to accommodate all signals necessary for videorecording and playback on a one-half inch wide tape using ten dualtracks in this manner.

Accordingly, the primary object of the invention is to provide a novelreversible tape transport system which is capable of rapid turn aroundwithout losing control of the tape, and having a minimum of inertiabeyond the unavoidable inertia of the roll of tape itself; to providesuch a transport system wherein a tape direction is quickly reversed,and the transducer shifted, in the order of one second, to minimizedisruption of viewing when the system is used in video recording; and toprovide such a system which is relatively simple and economical inconstruction, operation and maintenance.

Other objects and advantages of the invention will be apparent from thefollowing description, the accompanying drawings and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS I FlG. l is a somewhat schematic planview of a tape transport system embodying features of the invention;

FIG. 2 is a view showing the capstan, its drive shaft, and fragments ofthe takeup and supply rolls;

FIG. 3 is a somewhat schematic view showing the capstan, its synchronousmotor drive including the resonant damper and speed control switch, andmechanism for shifting the transducer to different tracks;

FIG. 4 is a partial perspective view showing details of the resonantdamper;

FIG. 5 is a diagram of the constant control ling movement of thetransducer head; and

FIG. 6 is a schematic wiring diagram.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, whichdiscloses a preferred embodiment of the invention, the tape 10, whichmay for example be magnetic recording tape, is shown coming from asupply roll 12 which is wound on a hub 13 supported on a rotatable axle14. This axle is in turn carried on a swinging arm 15 that is pivotallymounted to the base mounted at 17 to the deck or base of the transport.The tape 10 passes from the supply roll to a takeup roll 22 where it issupported and wound on a hub 23 having an axle 24 rotatably mounted onthe supporting arm 25. This am is also pivotally mounted to the base ordeck through the pivot hinge or pin 27.

Suitable one-way acting brakes (:not shown) may be provided for theaxles 14 and 24, to resist unwinding of the tape from the associated hubwith a limited force. When the hub is rotated in the opposite directionthe brake has no effect.

The tape is passed around the driving capstan 30 which has a resilientperipheral face 32, such as a rubber tire," which engages the backsurface of the tape and moves it from one roll to the other. The capstanis mounted on a drive shaft 33 which supports and rotates the capstan.The capstan incorporates a lower fixed or rigid guide flange 34 and anupper flange 35 which preferably is formed of somewhat flexible materialand is sectioned adjacent its outer edge, as by a number of slots, intoa plurality of spring sections 36 which tend to guide the upper edges ofthe tape downwardly, thus guiding the lower edge of the tape intocontact with the flange 34. This arrangement assures proper alignment ofthe tape, as when passing it across one or more magnetic transducers Tthat are mounted to contact the tape at one side of the capstan, andalso contributes to accurate placement of the tape on the takeup in thetype of configuration shown.

The capstan is driven by a synchronous motor 38 through a driveconnection such as the belt and pulley drive 39 which is shownschematically in FIG. 2. In the two-way configuration shown, this motoris reversible.

In accordance with the invention a means is provided holding thedeparture point of the supply roll 12 at a predetermined and constantspaced relation to the capstan, thereby causing the tape 10 to span agap from. its point of departure from the supply roll to its point ofinitial engagement with the peripheral face of the capstan. This spacingneed not be very large, and in practice a spacing of about 0.010 inchhas been found adequate. For this purpose a roller 40 is mounted forfree rotation on the end of an arm 42 that is in turn pivotally mountedat 43 to the deck. A medium force spring 45 is connected between a fixedpoint on the deck and the arm 42, and tends to pull the roller 40 intoengagement with the supply roll, and thus push the roll away from thecapstan, in the direction shown by the arrow in FIG. 1.

The Movement movement of arm 42 and roller 40 is controlled through afollowing arm 46, which is pivoted to the base at 47, and which has aforked end engaged around the axle 14, or some other suitable point onthe supply roll. The arm 46 carries a control cam 48 which engages aroller follower 49 on the arm 42. The cam is: contoured according to thedecrease in diameter of the roll 112 as successive convolutions of thetape are removed. The arm 46 and cam 48 thus function as a following andposition control means which maintains the roller 40 engaging theoutermost convolution of the tapeonthe supply roll, and holds this rollat an essentially constant spacing from the peripheral resilient face ofthe capstan. L.

Since the transport system preferably is intended to be bidirectional,the invention preferably includes a comparable control for the roll 22,since in the reverse direction of operation from that shown, it will infact function as the supply roll. Thus, there is a second roller 50carried on the end of an arm 52 which is pivotally mounted to the baseat 53. The roller 50 rides in contact with the outermost convolution oftape on the roll 22, and is urged against the roll by the force ofspring 55 connected between arm 52 and a fixed point on the base. Afollowing arm 56 is pivoted to the base at 57 and carries a furthercontrol cam 58 which engages a roller follower 59 on arm 52.

This system tends of course to move the takeup roll 22 away desired thatthere be pressure contact between the capstan and this roll in order toassure that the tape is placed smoothly and evenly on the takeup.Further, this contact may be used to rotate the takeup. Therefore, meansare provided to override the force and effect of the rollers 40 and 50,respectively, depending upon which side is functioning as the takeup.

A torque motor 60 having an output pinion or gear 62 is connected todrive a rack 63, which is in turn connected to an extension of thesupply roll mounting arm 15. Similarly, a torque motor 70 has a pinion72 meshing with a control rack 73 that is pivotally connected to anextension of mounting arm 25. Depending upon the desired direction ofrotation, one or the other of these torque motors is actuated to exertsufficient force to overcome the force of the corresponding. spring,roller and connected mechanism, and to urge the roll into pressurecontact with the capstan. in the condition shown torque motor 70 is thusenergized and produces pressure contact between the takeup roll 22 andthe capstan. Torque motor 60 at this time exerts no effective force onthe system. However, in reverse direction operation, torque motor 60overrides the roller 40 and its associated mechanism. while torque motor70 becomes ineffective and the roller 50 maintains the desired constantspacing between the tape departure point of roll 22 and the capstansurface.

1 16. 6 is a diagram of a suitable control for the system, shown forsimplicity as an AC control circuit. Power supply is indicated by thelegend, and the opposite terminals are shown grounded. A manuallyoperated start switch 80 (shown open) is connected to one element 820 ofa three pole double throw manual stop switch 82 (shown in normal orstart position). The start switch also provides power when closed to thecoil of a time delay relay 83. The blade 83a of this relay completes apower supply circuit directly to a second blade element 82b of the stopswitch, and this in turn applies power to the motor power line 84.

The third element 82c of the stop switch is connected to power supplythrough the relay'blade or contact 83a and thus is controlled by it. inthe normal position of the stop switch, the element 82a provides power(with the start switch closed) to a line 85 which forms a higher voltagesupply to one or the other of the torque motors 60 and 70. Also, line 85is arranged to receive power through the normally open contact of stopswitch element 82b in the closed position of the stop switch, providedrelay 83 is energized.

A dropping resistor 86 is connected from line 85 to a lower voltagesupply line 88. This line can also become a higher voltage supply viaits connection through the normally open contact of stop switch element820, also provided relay 83 is energized. I

A direction control latching relay 90 has four double pole contactswhich control the reversing circuits for motor 58, and for the torquemotors. Relay blades 90a and 90!) are arranged to reverse the polarityof one of the motor windings, through capacitor 91. Relay blades 90c and@041 control the power supply to torque motors 70 and 60, respectively,from either the high voltage line or the" normally low voltage line 88.in the condition shown, motor 70 is connected to the higher voltage andthus holds takeup roll 22 against the capstan, and motor 38 is rotatingthe capstan 30 counterclockwise, as viewed in FIG. 1. 1;

To reverse, the coil L ofthe -latching-relay isenergized, either throughthe manual reversing switch 94, or the automatically controlled switch(see also FIG. 1) which senses movement of arm 15correspondingltoanvempty supply roll 12. Changing direction back to thatshown is accomplished by energized coil 90R of the latching relay,either through manual switch 96 or the automatic switch 97 which isclosed by arm 25 when it reaches a position corresponding to an emptyroll 22.

On stopping the system, moving stop switch 82 to its stop position,opposite to that shown, switch element 821) maintains power to thehigher voltage line 35 through its normally open contact, and line 88 ischanged to the higher voltage through the normally open contact ofelement 820 Both torque motors thus receive higher voltage and hold bothroll 12 and 22 against the capstan. This prevents overrunning of thesupply roll as the system decelerates.

The start and stop switches are mechanically interlocked by conventionalmeans (not shown), such that actuating one moves the other to theopposite position. Thus start switch 80 will open when stop switch 82 isclosed. This interrupts the power supply to the coil of the time delayrelay. However a time delay device (not shown) holds the relay blade 83aclosed for a certain period of timepsufficient to permit the system tostop before blade 83a 'opens and interrupts the power supply to motor 38.and torque motors 60 and 70. After the transport is stopped,, bothrollers 40 and 50 are free to move their associate dlrolls 1 2 and 22away from the capstan, relieving its surface 32 from pressure-contactwith either roll.

During normal operation of the motor 38 at its synchronous speed thecapstan is rotated at a corresponding predetermined speed which producesthe desired constant velocity of the tape past the transducers T. inorder to to operate at a speed'significantly lower than synchronousspeed, such as in'a recordingdevice which provides for self-threading,the present invention provides a separate power and speed control forthe synchronous motor.

The electrical power supply is connected through a normal runningcircuit including line 84 and the speed selector means 100. This meansmay be in the form of a double pole single throw mechanical switch asillustrated, or may be in the form of any suitable electronic orelectrical switching device as may be desired.

The slow speed power circuit to the motor is connected by actuating theselector means 100 to complete a circuit through line 102 and aninterrupter means 103 which is controlled by a feedback deviceresponsive to the motor speed. The interrupter 103 conveniently is inthe form of a normally closed switch which has an internal spring loadtending to hold it in its closed position. The actuator arm or leaf 104of this switch extends into contact with a governor mechanism 105,details of which are shown in F 10. 3.

The rotor shaft of the motor 38 has fastened to it a spindle 107 whichis provided with a cross passage 108 receiving a the flyweight arm 110,an this arm is pivotally mounted about a transverse axis through acrosspin 111. A cam 112 is formed on the arm slightly to one side of thecrosspin, and this cam engages an actuator pin or rod 114. The pin 114is slidably mounted in the hub 107 along its axis of rotation andextends upward into engagement with the switch actuator arm 104.

The internal spring load of the switch 103 normally is sufficient topush pin 114 downward against cam 112. thus at rest and at speeds belowthe desired low speed motor operation. the flyweight arm 110 is urged tothe position shown in dotted lines in FlG. 3. The positions of the pinand cam are shown in the "at rest position in full lines.

As the motor reaches a predetermined speed at which the flyweight 110will rotate about its crosspin, the flyweight will move to the positionshown in full lines in FIG. 3, since the ends of the flyweight arm willtend to assume the largest radius that they can attain. This causes cam112 to push upward on the pin 114, opening the switch 103 and thusinterrupting the low speed power supply to the motor. As the motorslows, for example due to the load upon it, the flyweight arm willreturn to its dotted line position, and switch 103 will again close. Byappropriate selection of the length and mass of the flyweight arm, it ispossible to have the flyweight move between these two positions over arelatively small range of speed difference. This permits the interrupterin the low speed circuit to open and close again at speeds which arefairly close to each other, for example in the order of rpm. difference,thus it is possible to operate the synchronous motor at this lowerspeed, which is essentially the actuating speed of the flyweight arm110, without noticeable hunting.

FIG. 3 shows the precision motor drive system incorporating thesynchronous motor 38 receiving power from a suitable AC supply. Thissupply is usually 60 cycle AC although it should be recognized that insome locations either cycle or 50 cycle a AC is used commercially. Themotor shaft 115 is connected to the pulley, and it is this shaft whichhas been found to exhibit a vibratory output torque variation which isrelated to the frequency of the AC supply. For example, with a 60 cycleAC power supply the output torque variation has been observed at 120cycles per second, generally according to the regularly changingpolarity of the alternating current power input.

In accordance with the invention a resonant damping device is providedon shaft 115 in the form of a hub member 117 fixed to the shaft, forexample by tightening a set screw 118. Surrounding this shaft, coaxialwith the hub, is a ring 120 which is connected to the hub 117 by aplurality of compliant spoke members 122. These spoke members arefastened at opposite ends to the hub and to the ring respectively, andare preferably selected from flat strips of spring steel havingsufficient resilience to cause the hub-spoke-ring system to exhibit aresonant vibration characteristic at a frequency of approximately doublethe frequency of the AC power supply, for example 120 cycles per second.It has been found desirably to incorporate the shaft 115 as a part ofthe resonant damping device, by accurately tuning the damping mechanismwhile attached to the shaft 115. Since it is desirable to have thedamping device tuned as closely as possible to the desired resonantfrequency, it may be desirable to include some means for fine tuning ofthe resonant frequency of the system, and satisfactory results have beenobtained by providing a plurality of threaded screws 123 which arereceived in threaded holes at regularly spaced intervals (usually 120apart) on the ring 120.

Lock nuts 124 are provided to hold each screw in its adjusted position.By turning the screws it is possible to move their respective weightstoward or away from the axis of rotation of the device, and hence tochange the moment of inertia of the ring 120 by a slight amountsufficient to provide the desired accurate tuning.

The transducers T are carried in a head 125 mounted on a supporting post126 for movement transversely of the path of movement of the tape 10which is carried past the head on capstan 30. A track width is arelatively small fraction of the total width of the tape, for example ina typical embodiment the tape 10 has a width of one-half inch, and eachtrack width is 0.0l7 inch. Thus, the track or tracks followed by thehead occupy relatively small and spaced apart segments of the width ofthe tape, and the head 125 can be moved to different positions withrespect to the tape in order to follow different tracks as the tape istransported in one direction or the other between the supply and takeup.

For purposes of moving the heads simultaneously, a selector device isprovided in the form of the supporting rod or post 126 cooperating witha cam follower 128, and the post is mounted for vertical movement, forexample in a suitable tubular holder or the like (not shown). A lightspring is adapted to press upward against the post 126 urging it to itsupper limit position.

The cam follower 128 engages a barrel type cam 130 which 7 is mountedadjacent the post 126, being secured to a rotatable shaft 132 which hasfixed to it a ratchet wheel 133. The pawl 134, which may be controlledfor example by a solenoid 135, is arranged to rotate the ratchet wheeland hence the cam 130, by a predetermined angular amount. Preferably, aconven-' tional secondary pawl (not shown) is provided to hold theratchet wheel in any given position.

FIG. 5 is a graphic view of the control surface of cam 130, illustratingten steps 130a-130j, any one of which may be engaged with the follower128 to locate the post and the heads in a corresponding verticalposition. As will be obvious from FIG. 3, a counterclockwise rotation ofcam 130, as viewed from above, will provide a cam action on the follower128 tending to push it downward in a step-by-step fashion. After thefinal or lowermost step, there is a return and a ramp 131 which willguide the follower back to its upper most position,

130a in response to urging of the spring.

As shown in FIGS. 3 and 6, when the flyweight operated switch 103 isclosed, selector is in the position shown, and the transport isoperating, a signal appears on the line 102, and this signaLindicatesslowing of the motor-capstan assembly. This signal is applied throughline 140 to the head shifting control unit 142, which in turn isconnected to actuate the solenoid 135. As the motor and capstandecelerate in a reversing operation, the head shift control thusreceives a signal as the capstan is almost stopped. Due to inherentdelays in the head shifting controls and mechanism, this causes the headto be moved to a different track immediately as the motor and capstanreverse.

Since actuation of switches 95 or 97 will immediately energize theappropriate coil 90L or 90R of the latching relay, the relay blades 90cand 90d will shift to place a higher voltage on whichever torque motor60 or 70 waspreviously energized through the lower voltage line 88. Theroll functioning as a supply thus is immediately moved into contact withthe capstan as it decelerates, preventing the supply from overrunning.The roll acting as a takeup will begin to move away from the capstan, asits torque motor is now connected to the lower voltage supply. However,the takeup has been driven by the capstan up to that time, hence itsinertia will keep the tape taut as it leaves the slowing capstan.

The motor 38 decelerates rapidly, since reversing polarity of one of thewindings effectively causes a dynamic braking of the motor and therotating parts have a relatively low mass. The motor quickly reacheszero velocity and starts accelerating in the opposite direction. Due tothe low inertia of the system, this change in direction is rapid, only afraction of a second being required to change from full speed in onedirection to the other. In this time the head is shifted to anothertrack, hence there is only a short interruption in the output (or input)signals from the tape. The head remains following the previous trackduring deceleration, thus thus recording or reading of a signal from thethat track continues up to the moment of reversal. By the time the headis then shifted, the tape is accelerating in the opposite direction andrecording or reading resumes immediately on the next track, with aminimum of interruption, and without reading or recording over the sametrack in opposite directions. This is a particular advantage inlongitudinal recording or programs such as video signals, where minimuminterruption is desired.

While the form a of apparatus herein described constitutes a preferredembodiment of the invention, it is to be understood that the inventionis not limited to this precise form of apparatus, and that changes maybe made therein without departing from the scope of the invention.

We claim:

1. In a tape transport system comprising:

a pair of rolls providing a supply and a takeup for flexible tape;

a rotatable capstan arranged to engage the tape over a section of itsperipheral face and to drive the tape from one of said rolls to theother;

and means mounting said rolls for movement toward and away from saidcapstan in compliance with the change in diameter due to buildup of tapethereon;

a head and at least one transducer mounted therein to scan a track alongsaid tape which track has a width which is only a fraction of the tapewidth;

means supporting said said motor for selective movement to differentpositions across the width of said tape;

a selector device controlling the position of said supporting means;

the improvement comprising a reversible drive motor coupled to rotatesaid capstan;

a speed sensing switch means driven by said motor;

control means to reverse said motor rapidly when tape on the supply rollis depleted to a predetermined minimum and to actuate said selectordevice to initiate changing of said head to a different track location;

and said control means including an operating connection from saidswitch means to said selector device to provide a signal in response toslowing of said motor sufiiciently to initiate a change in position ofsaid head.

2. A tape transport system as defined in claim 1, wherein:

said rolls are mounted for independent movement toward and away fromsaid capstan in compliance with the change in diameter due to transferof tape from one roll to the other;

said control means include means responsive to stopping of said motorand operative to move both said rolls into contact with said capstanduring stopping thereof and then to hold both said rolls spaced fromsaid capstan once its rotation has ceased.

227 33 UNITED S'ITATES PATENT OFFICE CERTIFICATE OF CORRECTION PatentNo. 3,550,985 Dated December 29, 1970 Inventor) Don C. Barnett andKingston E. Ganske It is certified that error appears in theabove-identified paten and that said Letters Patent are hereby correctedas shown below:

Column 1, line 22, delete "the" before "thus" Column 1, line 29, delete"rather" between "been" and "customary" Column 2, line 24, the phrase"mounted to the base" should deleted Column 2, line 68, delete"Movement" Column 4 ,line 40, delete the second "to" Column 4, line 62,at the end of the line, delete "a Column 4, line 63, "an" should be -andColumn 6, line 58, delete the second "thus" Column 6, line 67, "form aof apparatus" should be --form I apparatus-- Column 7, line 10,"supporting said said motor" should be supporting said head Column 8,line 8, delete the second occurrence of the phr. "to hold the" Column 8line 10, "and" should be deleted.

Column 8, line 11, "said means control means" should be --said controlmeans-- Signed and sealed this 1 7th day of August I 971 (SEAL) Attest:

EDWARD PLFLEI'CHERJR. WILLIAM E. SGHUYLER, JR. Attesting OfficerCommissioner of Patents

